Bad Air Days in Monongalia County, West Virginia: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 905 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (50% particle days).

The bad-air season here

Most bad days here fall in June. Averaged over 2016 to 2025.

Is a purifier worth it here?

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

Better or worse than it was

In 2000 to 2009 this county averaged 14 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2025, with 1 bad day on 272 monitored days.

Date	AQI	Main pollutant
2023-06-29	169	PM2.5
2025-06-12	105	Ozone
2025-03-13	97	Ozone
2018-06-16	93	Ozone
2023-04-13	93	Ozone

The air on a normal day

Across 2,749 monitored days from 2016 to 2025, the air in Monongalia County rated Good on 84% of them, more often than the 72% typical of monitored counties, and Moderate on 16%. The median day sat at AQI 40; one day in ten went above 55.

The pollutant setting the AQI on an ordinary day here:

ozone74%2,030 days
fine particles (PM2.5)26%719 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	272	217	54	1	0	42	105
2024	267	211	56	0	0	43	93
2023	277	227	49	1	1	42	169
2022	280	250	30	0	0	37	77
2021	282	225	57	0	0	39	80
2020	274	248	26	0	0	39	90
2019	277	237	40	0	0	41	74
2018	278	236	42	0	0	38	93
2017	282	242	40	0	0	40	90
2016	260	216	44	0	0	38	74
2015	254	184	68	2	0	43	133
2014	261	201	60	0	0	41	90
2013	248	183	64	1	0	40	115
2012	261	167	88	6	0	44	150
2011	257	170	86	1	0	44	119
2010	259	143	109	7	0	49	143

*2025 may be a partial year in EPA's file.

Elsewhere in West Virginia

Ohio County1/yr
Berkeley County1/yr
Hancock Countyunder 1/yr
Wood Countyunder 1/yr
Marshall Countyunder 1/yr
Kanawha Countyunder 1/yr
Cabell Countyunder 1/yr
Brooke Countyunder 1/yr

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day, and on why a purifier does not touch ozone in smoke vs ozone.